Converting Russian Calculator to 9v DC

@==>*steve*

Why would you say the display might require 90V? It appears to me to be an LED display and while I am not any kind of expert on displays, I have never encountered an LED display that required more than 12V. The fact that there are 7 wires leading from the PS board to the main board certainly suggests a more complex supply than I would have thought were required, but the transformer secondary appears to be a simple center-tapped design; and I would guess from the vintage if a HV rail were required it would have been achieved by a third winding on the transformer. It does appear that two white wires run directly from the primary side to the PS board, and I cannot even begin to explain why they would be there; so all of this is conjecture on my part, I don't have a calculator collection ;-) but I am intrigued both by your assertion that the display might be HV, AND the fact that there are 7 wires running from the PS board to the main board.

PLEASE expound a bit on your thoughts/experience with vintage calculator designs; I am not questioning you, only very, very curious. By the mid 1980's SMPS power supplies were certainly available, but were not common (to my knowledge) in anything other than PCs and a select few audio amplifiers, but I guess it is possible the transformer is being switched not line driven, but that seems awfully complicated for a calculator of that period.

Again, please expound a bit!

Fish

 

It is a vacuum fluorescent display, and while most modern ones do have onboard converters to step it up to the appropriate voltage, this board appears far too simple in construction - likely there is a higher-voltage tap on that transformer that is feeding it.

That being said, it is in the realm of feasibility to construct a 220V step-up inverter, possibly being fed from a 9.6V high-capacity rechargeable, and using that - that way the original circuit would require absolute minimal modification. However, as Steve said, the battery life most certainly would not be stellar.

 

@Solidus==> Thanks, those are VERY cool! I was completely unaware of that technology, so of course I had to go order a few for my display collection Now if I could just find something that needed a display....hehe.

Fish

 

Thats a nice piece of kit - probablt worth a few bob now. Personally I wouldnt risk damaging it, but if you really want to, I would suggest plugging it in and (carefully) measuring the voltages at key points which would be across the transformer output and the display - Its just a matter of taking a methodical approach and figuring out what needs done at each point